Cold air slipping through the gaps around a window is one of the most common reasons a room never feels warm, even when the heating is on. Draught proofing seals the gaps around doors, windows and floors to stop unwanted cold air getting in, and cutting draughts reduces heat loss and heating demand. It is one of the cheapest energy saving jobs in the home, and most of it is simple DIY. The hard part is not the fitting. It is choosing the right method for the window in front of you, because a strip that works beautifully on a modern casement can fail completely on a sliding sash.

So what is the best way to draught proof windows? There is no single winner. For most opening casement windows, brush or wiper strips are the best all round choice, because they last longer than foam and still cost very little. For sliding sash windows, brush strips are again the answer, because foam strips do not work well on them. For a window that never opens, a bead of silicone sealant beats every strip. And for single glazed period windows, secondary glazing is the biggest single upgrade, cutting heat loss by over 60 per cent according to Historic England.

What is the best way to draught proof windows? The short answer

If you want the answer in one line, it is this: use brush or wiper strips on windows that open, silicone sealant on windows that do not open, and secondary glazing on single glazed windows you want to keep. The table below ranks every method in this guide so you can compare them at a glance.

Find the draught before you buy anything

The most common draught-proofing mistake is buying strips before knowing where the air is coming in. A window can leak around the frame, between the sash and the frame, through the meeting rails of a sash window, or around a loose bead holding the glass. Each leak needs a different fix, and sealing the wrong place wastes money while the real gap keeps leaking.

The Energy Saving Trust recommends four simple checks. Look for visible light under and around doors and windows; if you can see daylight through a gap, cold air is using it. Listen for rattles and whistling on windy days. Feel for moving air with the back of your hand around the frame, the hinges and the meeting rails. And watch the curtains; curtains moving when the window is shut is a good indicator of a draught.

Do this check on a cold, windy day, and check every window in the room, not just the one you suspect. Mark each gap lightly in pencil so you know exactly where the strip or sealant has to go. Also check whether the window closes squarely: a casement that has dropped on its hinges leaves a wedge shaped gap that no strip can fill until the hinges are adjusted, and a sash with a broken cord or swollen frame needs repair before any draught-proofing will hold. Historic England makes the same point for older windows: repair comes first, and like-for-like repairs will not usually need consent. A survey like this also tells you what is the best way to draught proof windows in each room, because the right method follows the gap.

Self-adhesive foam strips: the cheapest start

Self-adhesive foam strips are the simplest form of draught-proofing. They are lengths of compressible foam with a sticky back that you press around the frame of a window that opens, so the foam is squeezed when the window closes and fills the gap. They are cheap and easy to install, which is why they are the first product most people reach for, and they suit opening casement and tilt and turn windows where the gap is even and the window closes squarely.

The weakness is lifespan. The Energy Saving Trust is direct about it: foam strips are cheap and easy to install but may not last long. The foam compresses permanently over time, the adhesive dries out, and the strip can peel away from the frame, especially on a window opened and closed every day. Expect to replace foam strips regularly, and check them each autumn before the cold weather arrives.

Sizing is the other pitfall. The strip must be the right size for the gap. Too big and it gets crushed, the window may not close, and the foam will wear out faster. Too small and a gap remains, so the draught carries on as before. Measure the gap at several points around the frame, because gaps are rarely even. Foam strips do not work well on sliding sash windows: the sliding action rubs the foam, crushes it and drags it out of place. For sash windows, brush strips are the right product.

Brush and wiper strips: the best all round choice

Brush and wiper strips are metal or plastic strips with brushes or wipers attached, fixed around the frame of a window that opens. When the window closes, the brush or wiper presses against the frame and blocks the air. They cost a little more than foam strips, but they last longer, which is why they are the best all round choice for windows that open.

These strips suit almost every opening window: casements, tilt and turn windows, and, most importantly, sliding sash windows. The Energy Saving Trust specifically recommends brush strips for sliding sash windows, where foam strips do not work well. On a sash, brush strips are fitted to the staff beads and parting beads so the brushes seal the sliding surfaces without stopping the sash moving. Metal windows can often be economically repaired and draught-proofed in the same way, according to Historic England.

Fitting takes a little more care than sticking foam in place. Some brush strips screw to the frame, some are self-adhesive, and some fit into a groove routed into the timber. Screwed strips hold best on windows opened daily. The same sizing rule applies: too big and the strip gets crushed and the window may not close, too small and a gap remains. For period and listed homes, brush strips are usually the right first step before anything more invasive, and Historic England recommends repairs and draught-proofing as the first route for older windows. A well fitted brush strip system cuts the draught without changing how the window looks from the street.

Silicone sealant: for windows that never open

Silicone sealant is the right answer for a window that does not open. It is a flexible bead of sealant run along the gap between the glass and the frame, or between the frame and the wall, where air is leaking through a joint that never needs to move. The Energy Saving Trust recommends it specifically for windows that do not open, such as fixed lights, picture windows and the non-opening side of a bay. Because the sealant cures into a flexible rubber bead, it moves slightly with the frame as timber expands and contracts, which is why it lasts longer than a foam strip in the same place.

Preparation decides whether it works. Old sealant, paint flakes and dust must be cut away and the joint cleaned before the new bead goes on, or the sealant will peel away from a dirty surface within weeks. Cut the nozzle to match the width of the joint, run a steady bead, and smooth it so it fills the gap fully. Check the bead each year; if it has cracked or pulled away from one side, cut it out and redo that length rather than layering fresh sealant over the old.

The one hard rule is never to use sealant on a window that opens. A bead across an opening joint will glue the window shut, and forcing it open will tear the seal and damage the paint and timber. Painted shut sash windows are common in older homes, and they need freeing and repairing before any draught-proofing, not sealing in place.

Secondary glazing: the biggest upgrade for single glazed windows

Secondary glazing is a second pane of glass, or a clear acrylic panel, fitted inside the existing window, leaving a gap of still air between the two panes. It is the biggest single draught and heat loss upgrade for a single glazed window, and Historic England recommends it alongside repairs and draught-proofing as the main route for older windows. In some situations secondary glazing can bring even greater energy efficiency improvements than double glazing, and it can reduce heat loss by over 60 per cent.

Secondary glazing suits single glazed sash and casement windows, especially in period homes where replacing the original window would harm the character of the building or need consent. Historic England is clear that older windows can be as energy efficient as new ones, and that repair is better than replacement. A secondary glazing unit keeps the original window, adds a discreet inner pane, and can be removed later without damage. For the full cost picture, see our guide to secondary glazing costs in the UK.

There is one rule that catches people out. Where secondary glazing is installed, do not draught-proof the original window, to prevent condensation and mould. The gap between the original window and the secondary pane needs a small amount of air movement, and sealing the outer window traps moist air in that gap. If the secondary glazing is fitted properly, it does the draught-proofing job itself.

On lifespan, secondary glazing is a long term investment. The frame and fixings last for decades with normal care, but sealed glazed units do not last forever: double or triple glazed units need replacing roughly every 30 years, against 60 to 100 years for single glazed windows, according to Historic England. That is still far longer than any strip or film, and it compares well with replacement windows, whose uPVC frames have a service life under 25 years against well-maintained traditional windows over 100 years.

Window film: a cheap seasonal fix

Window film is a clear plastic film stretched across the window frame and shrunk tight with a hairdryer, creating a second layer of still air over the glass. It is cheap, easy to fit, and needs no tools beyond scissors, tape and a hairdryer, which makes it popular in rented homes and as a quick winter fix for single glazed windows where the glass itself is cold.

Be honest about what film does and does not do. It does not seal a gap around the frame. If air is leaking through the frame joints or between the sash and the frame, film stretched over the glass will not stop it, and the film can even billow or peel where air gets behind it. Film is a fix for cold glass, not a substitute for strips or sealant on a leaking frame. Fit the strips first, then add film over the glass if the room still feels cold.

Film is also a seasonal product. Treat it as a fix for one heating season: fit it in autumn, take it down in spring, and replace it the next year. The film can tear, cloud or lose its grip over time. Keep the cost in perspective: film is cheap, so replacing it yearly is not a burden, but do not expect it to do the job of secondary glazing, which reduces heat loss by over 60 per cent and lasts for decades.

Heavy curtains, blinds and shutters: the night time layer

Heavy curtains, insulated blinds and shutters do not seal a gap, but they significantly reduce heat loss through the glass, and Historic England recommends them as part of the package for older windows. A thick curtain drawn across a window at night puts a layer of still air between the room and the cold glass, and closing shutters at night has the same effect. Used together with draught-proofing strips, they cover both routes of heat loss: the air leaking around the frame and the heat escaping through the glass.

Fit matters here. A curtain only works if it covers the whole window and hangs close to the wall, with as little gap as possible at the top, sides and bottom. A short curtain that stops at the sill, or a thin curtain that lets air flow behind it, does little. A pelmet or a curtain track fitted close to the wall above the window stops warm air dropping behind the curtain and pooling against the cold glass. Insulated blinds work the same way: they need to fit the window closely, or warm air slips around the edges.

Curtains and shutters are a complement to draught-proofing, not a replacement for it. A thick curtain over a window with a wide gap around the frame will still let cold air into the room, because the air enters behind the curtain. Seal the frame first, then add the curtain as the night time layer. The two together are worth more than either on its own.

Professional draught-proofing: when to pay someone else

Professional draught-proofing means an installer seals every window, door and floor gap in the house with the right materials in the right places. The Energy Saving Trust says professional draught-proofing saves more energy because the installer knows the right materials and where to use them. That is the core of the case for hiring someone: it is not the labour you are buying, it is the judgement about which strip, sealant or bead goes where.

The cost is around £250 for a whole house, according to the Energy Saving Trust, and DIY is cheaper. That figure covers windows and doors together, so a house with many windows and doors will cost more and a small flat will cost less. Get three quotes before choosing an installer, and check that the installer is listed on TrustMark, the government-endorsed quality scheme, which the Energy Saving Trust recommends. You can find certified installers through TrustMark.

Hire a professional when the windows are hard. The Energy Saving Trust says DIY is straightforward if you are confident with simple DIY, but older homes with traditional features are harder and need professional help. That covers sliding sash windows with worn beads, metal windows that need specialist strips, windows that have dropped on their hinges, and any home where several windows need repair before they can be sealed. For the wider picture on sealing doors as well as windows, see our guide on how to stop draughts from windows and doors.

What not to block

Draught-proofing goes wrong when it blocks air that the house needs. The Energy Saving Trust is clear that good ventilation is still essential even in a well sealed home, and that you should not block vents, chimneys or airflow needed for safety and air quality.

First, trickle vents. These are the small slots in the top of modern window frames that let a controlled trickle of fresh air into the room. They are there to control moisture and keep the air fresh, and they must stay open. If a trickle vent is noisy or draughty, clean it and check the cover closes properly, but do not tape over it or fill it with sealant.

Second, rooms with open fires or open flues. Do not draught-proof gaps to rooms where ventilation matters, because a fire needs air to burn safely and a flue needs air to draw properly. The same applies to flueless gas appliances, which need ventilation to operate safely. If you are unsure whether an appliance needs ventilation, check the appliance manual or ask a qualified engineer before sealing the room.

Third, kitchens, bathrooms and utility rooms, where moisture is produced. These rooms need air movement to carry steam and moisture out of the house, and sealing them tightly without another way for moisture to escape leads to condensation, damp and mould. Keep the extractor fan working, keep the trickle vent open, and seal the gaps in the living rooms and bedrooms first, where the comfort gain is greatest and the moisture risk is lowest.

Fourth, chimneys. An unused chimney is a big source of draughts, and sealing it saves around £45 a year in Great Britain and £60 in Northern Ireland, according to the Energy Saving Trust. But a chimney that is still used, or that serves a gas appliance, must not be blocked. Use a removable chimney balloon or a proper cap fitted by a professional, never a permanent seal on a working flue.

How much does draught proofing windows cost, and what does it save?

The cost depends on how many windows you have and whether you do it yourself, but the published figures give a clear range. Professional draught-proofing of windows and doors costs around £250 for a whole house, according to the Energy Saving Trust, and DIY is cheaper. The materials for a single window, a pack of foam or brush strips or a tube of silicone sealant, cost very little compared with that professional figure, which is why DIY draught-proofing is one of the best value energy saving jobs in the home.

The saving figure is also from the Energy Saving Trust: draught-proofing windows, floors and doors saves around £55 a year in Great Britain and £80 in Northern Ireland. That is the saving for the whole package, not for one window, and it is a modest figure next to some of the claims seen online. Do not believe anyone who tells you draught-proofing will halve your heating bill; the published figure is around £55 a year in Great Britain, and it should be weighed honestly against the low cost of the work. Cost is part of what is the best way to draught proof windows in any home, because the cheapest method that lasts is usually better value than the cheapest method on the shelf.

There are two useful comparisons. Draught-proofing an unused chimney saves around £45 a year in Great Britain and £60 in Northern Ireland, so a chimney balloon is worth doing alongside the windows. And turning the thermostat down from 22C to 21C saves £120 a year in Great Britain and £80 in Northern Ireland, more than twice the draught-proofing saving, so the cheapest energy saving step of all is still the thermostat. Draught-proofing makes the house comfortable at that lower temperature, which is why the two work well together.

Help with the cost is available. The Warm Homes Plan is set to invest close to £15 billion, with fully funded support for people on low incomes to install draught proofing, and low and zero-interest loans for homeowners regardless of income. Check the Energy Saving Trust advice pages for the current support available in your area before you pay for the work yourself.

The verdict: what is the best way to draught proof windows for your home

Match the method to the window, and you will get the best result for the least money. Start by finding the draughts with the light, sound and hand checks, then work through the guide below.

If you have modern casement or tilt and turn windows that open, fit brush or wiper strips. They cost a little more than foam and last longer, and they are the best all round choice for a window that is opened every day. Foam strips are a fine stopgap if money is tight, but budget to replace them regularly.

If you have sliding sash windows, fit brush strips and do not waste money on foam, which does not work well on a sliding sash. Repair the sash first if it sticks, rattles or will not close squarely, and consider secondary glazing if the glass is single glazed and the room is still cold. Our guide to how to make old windows less draughty covers the sash-specific repairs and fixes in more detail.

If you have a window that never opens, run a bead of silicone sealant along the leaking joint and leave the opening windows to the strips. If you have single glazed period windows you want to keep, secondary glazing is the biggest upgrade available, cutting heat loss by over 60 per cent, and it preserves the original window. Remember the one rule: where secondary glazing is installed, do not draught-proof the original window.

If you rent, or you want a quick fix before winter, window film over the glass plus foam strips on the frame will make a real difference for very little money. Add heavy curtains for the night time, keep the trickle vents open, and leave the kitchen and bathroom gaps alone. If the house has many windows, period features, or windows that need repair first, get three quotes and hire a TrustMark listed professional for around £250 for the whole house.

Frequently asked questions

What is the cheapest way to draught proof windows?

Self-adhesive foam strips are the cheapest way to draught proof windows, and a tube of silicone sealant is nearly as cheap for a window that never opens. Foam strips cost very little and need no tools, but they may not last long, so they are best as a first step or a stopgap. If you want the cheapest method that also lasts, brush or wiper strips cost a little more than foam and last longer, which makes them better value over time. The question behind the question is what is the best way to draught proof windows on a tight budget, and the answer is foam strips now, brush strips when you can, and a professional quote for the whole house if several windows need work.

Do draught excluder strips work on sash windows?

Foam strips do not work well on sliding sash windows, because the sliding action rubs, crushes and drags the foam out of place. Brush strips do work on sash windows and are the product the Energy Saving Trust recommends for them. Brush strips are fitted to the staff beads and parting beads so they seal the sliding surfaces without stopping the sash moving. If the sash is warped or the cords are broken, repair it first, because no strip can seal a window that does not close properly.

Can you draught proof windows without replacing them?

Yes. Older windows can be as energy efficient as new ones, according to Historic England, and repair is better than replacement. Draught-proofing strips, silicone sealant and secondary glazing all improve an existing window without replacing it, and like-for-like repairs will not usually need consent. Secondary glazing can reduce heat loss by over 60 per cent and can in some situations bring even greater energy efficiency improvements than double glazing. Replacement should be the last resort, not the first step.

Does window film stop draughts?

Window film helps with cold glass but does not stop draughts through the frame. The film creates a layer of still air over the glass, which reduces heat loss through the pane, but air leaking around the frame, between the sash and the frame, or through the meeting rails will carry on leaking behind the film. Seal the frame with strips or sealant first, then add film over the glass if the room still feels cold. Treat film as a cheap seasonal fix, not a substitute for draught-proofing the frame.

Should I draught proof a window with secondary glazing?

No. Where secondary glazing is installed, do not draught-proof the original window, to prevent condensation and mould. The gap between the original window and the secondary pane needs a small amount of air movement, and sealing the outer window traps moist air in that gap. The secondary glazing does the draught-proofing job itself, so leave the original window to breathe and check the secondary unit seals properly instead.

When should I hire a professional to draught proof my windows?

Hire a professional when the windows are hard: older homes with traditional features, sliding sash windows that need repair, metal windows, windows that have dropped on their hinges, or a whole house that needs doing at once. The Energy Saving Trust says DIY is straightforward if you are confident with simple DIY, but older homes with traditional features are harder and need professional help. Professional draught-proofing saves more energy because the installer knows the right materials and where to use them, and it costs around £250 for a whole house. Get three quotes and choose an installer listed on TrustMark, the government-endorsed quality scheme.

Sources

• Energy Saving Trust: Draught-proofing: draught-proofing strips, sealant, sash windows, professional costs around £250, savings around £55 a year in Great Britain and £80 in Northern Ireland, Warm Homes Plan close to £15 billion, ventilation rules.
• Historic England: Windows: older windows as efficient as new ones, repair better than replacement, secondary glazing reducing heat loss by over 60 per cent, do not draught-proof the original window where secondary glazing is installed, shutters and curtains, service lives of uPVC and traditional windows.
• TrustMark: government-endorsed quality scheme for finding certified installers, recommended by the Energy Saving Trust.